Have you found a place / occasion yet? I know that for myself - having a date is the only way to actually prepare slides and get ready. Happy to look at the argument you are planning to make and circulate to friends. I'm on the board of the OpenCourseWare consortium, and we have staff that helps institutions with these presentations.
Hands-in-dirt: give a speech!
I have already invited to some occasions to give speech on OpenCourseWare. I have to prepare well and remember to write down the arguments I present, people's reactions and counterarguments.
By practicing well, I can convince people better.